This invention relates to an alarm system for detecting intruders in buildings, houses, factories, etc. and generating an alarm in response to the intrusion detection.
The intruder detection systems used so far include the infrared beam transmitter/receiver which produces an alarm signal when the beam is interrupted and the infrared detector which produces an alarm signal upon detection of an infrared radiation from an intruder. Examples of the conventional alarm systems of the latter type are disclosed in U.S. Pat. Nos. 3,760,399; 3,928,843; 3,703,718; etc. In either type of system, in order to cover the whole building or whole area to be guarded, such detection systems connected to the controller by their own lines are located along the possible invasion paths.
Such distributed alarm systems require, besides a large number of signal lines, a power line to feed electric power to each detector. Therefore, installation is very expensive and sometimes spoils the appearance of buildings.
It is an objective of the present invention to provide an alarm system which has a simplified wiring and installation compared to the aforementioned prior art devices.